The genus Viola is one of 22 genera
in the family Violaceae, which contains over 900 species. Hybanthus
is the next most common genus in North America and includes the green violet.
Radford et.al. (p.234) gives the following
key for distinguishing between these two genera.
"-Petals green; calyx about equaling corolla;
fruit 1.5-2 cm long; seed 3 mm or more long............Hybanthus -Petals not green; calyx not more
than 1/2 a long as corolla, or more and corolla greatly exceeding
10 mm; fruit 1.3 cm or less long; seed less than 3 mm long..........................................................................................Viola."

The numerous species (~500)
in Viola are commonly known as the violets and are usually easy
to recognize by their distinctively shaped leaves and flowers. The
flowers have five sepals and five petals, with one lowered and scoop-like.
The anthers of the five stamens cluster around the base of the pistil,
which is solitary and has a club-like style and stigma (Grimm,
p.173).

Identification of Species: Because the genus Viola contains 500 species,
many of which hybridize readily, identification of individual species can
be quite difficult. Radford et.al. (p. 234
- 236) gives a key for distinguishing between the species listed above.
The leaves of some violets make them easier to distinguish for the novice.
For example, V. pedata and V. sagittata, two species of the
so-called "acaulescent blue violets" have very distinctive leaves.
Pedata's leaves are divided into narrow segments and palmate, while
sagittata's leaves are shaped like arrows (see below). Experts
warn against using leaf blade characteristics as a classifying feature,
however, because the effects of hybridizations and environmental conditions
can lead to false identifications (McKinney p.5).
V. pedata leaf
V. sagittata leaf
drawing by M. Bugbee
drawing by M. Bugbee

General Information: The violets have historical and economic importance
resulting from their beauty and from the compounds they contain.
Their cultivation in gardens (especially the Parma violets and the pansies)
dates back for centuries. Napoleon used them as a political
and romantic symbol, and they are prominent in literature and folklore.
The Romans and others much more recently have cited the medicinal qualities
of the violets. They are high in vitamin A, salicylic acid, and a
compound called violine, and have been used for headache relief, as laxatives
and diuretics, and as expectorants (Coon, 1977).